Question

Which of the following elements has the greatest difference between the first and second ionization energies: C, Li, N, Be? Explain your answer.

Short answer

Lithium (Li) has the greatest difference between the first and second ionization energies.

Step-by-step solution

Understand Ionization Energies

Ionization energy is the energy required to remove an electron from an atom. The first ionization energy is the energy needed to remove the first electron, and the second ionization energy is for removing the second electron. Generally, the second ionization energy is higher than the first because it becomes more difficult to remove an electron after one has already been removed.

Consider the Periodic Trends

Elements tend to have higher ionization energies in the following order: Increases across a period (left to right) and decreases down a group (top to bottom). The difference between the first and second ionization energy is related to the stability of the resulting electron configuration after the first electron is removed.

Analyze Each Element

For Li, the configuration after the first ionization (Li+) is a stable noble gas configuration (He). For Be, the configuration after the first ionization (Be+) becomes more stable because it leaves Be+ with a filled s-orbital. For C and N, removing the first electron does not result in a noble gas configuration.

Determine Largest Difference

Lithium experiences a very large increase in ionization energy between the first and second ionization because the first ionization results in a stable noble gas configuration (He), making it extremely difficult to remove a second electron.

Key concepts

Periodic Trends

Periodic trends refer to patterns that emerge when looking at the periodic table. These trends help in understanding how different elements behave in terms of their physical and chemical properties. One important trend is ionization energy, which is the energy needed to remove an electron from an atom. In general, ionization energy tends to increase as you move from left to right across a period, due to the increased nuclear charge which holds electrons more tightly. On the other hand, it tends to decrease as you move down a group because the electrons are further from the nucleus and are shielded by inner electron layers.

With periodic trends, we can predict how difficult it might be to remove an electron from an atom, just by looking at its position on the periodic table. Elements on the far right, near the noble gases, usually have high ionization energies. Conversely, elements on the far left, such as alkali metals, have lower ionization energies and tend to lose electrons more easily.

Electron Configuration

Electron configuration describes how electrons are distributed in an atom’s orbitals. It is a key concept when discussing ionization energies. An atom’s electrons fill up energy levels starting from the lowest available level. The configuration is usually noted using numbers and letters, such as 1s², 2s², etc., representing the different shells and subshells.

Knowing the electron configuration of an element helps us understand its chemical behavior and reactivity. For instance, lithium (Li) is very reactive because after losing one electron it achieves a stable electron configuration. This makes its first ionization energy relatively low, but as the electron configuration adjusts to match a noble gas (helium, in this case), removing a second electron becomes quite hard. This is due to the significant stability the atom gains after the first ionization.

• 1s² configuration is especially stable because it represents a filled shell.
• Transitions between filled and partially filled subshells have distinct energy requirements, impacting ionization energy.

Noble Gas Configuration

Noble gas configuration refers to the electron arrangement that mimics that of a noble gas, the group of elements found at the far right of the periodic table. Noble gases like helium, neon, and argon have their outermost energy levels completely filled, making them extremely stable. Achieving a noble gas configuration is a driving force behind many chemical reactions.

When an element achieves a noble gas configuration through ionization, it often possesses enhanced stability. This is particularly evident with elements like lithium (Li). Li, after losing one electron, replicates the electron configuration of helium. At this point, the element becomes much more stable, which significantly increases the energy needed to remove any additional electrons. This sharp increase in required energy is a hallmark of a stable noble gas configuration.

• Noble gas configuration results in minimal reactivity because of the stability associated with a filled outer shell.
• Elements in the same group trend toward achieving this stable configuration through gain, loss, or sharing of electrons.